Argparse started raising ArgumentError exceptions
when the same parser is added twice. Therefore, we
perform the addition only if the parser is not there
already
Port match syntax to our unparser
* Add two no-op jobs named "all-prechecks" and "all"
These are a suggestion from @tgamblin, they are stable named markers we
can use from gitlab and possibly for required checks to make CI more
resilient to refactors changing the names of specific checks.
* Enable parallel testing using xdist for unit testing in CI
* Normalize tmp paths to deal with macos
* add -u flag compatibility to spack python
As of now, it is accepted and ignored. The usage with xdist, where it
is invoked specifically by `python -u spack python` which is then passed
`-u` by xdist is the entire reason for doing this. It should never be
used without explicitly passing -u to the executing python interpreter.
* use spack python in xdist to support python 2
When running on python2, spack has many import cycles unless started
through main. To allow that, this uses `spack python` as the
interpreter, leveraging the `-u` support so xdist doesn't error out when
it unconditionally requests unbuffered binary IO.
* Use shutil.move to account for tmpdir being in a separate filesystem sometimes
